linux-kernel - [PATCH 30/38] perf symbols: Avoid segfault in elf

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Message-Id: <1344883039-13495-31-git-send-email-acme@infradead.org>
Date:	Mon, 13 Aug 2012 15:37:11 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org,
	Cody P Schafer <cody@...ux.vnet.ibm.com>,
	David Hansen <dave@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...hat.com>,
	Matt Hellsley <matthltc@...ibm.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 30/38] perf symbols: Avoid segfault in elf_strptr

From: Cody P Schafer <cody@...ux.vnet.ibm.com>

If we call elf_section_by_name() with a truncated elf image (ie: the
file header indicates that the section headers are placed past the end
of the file), elf_strptr() causes a segfault within libelf.

Avoid this by checking that we can access the section string table
properly.

Should really be fixed in libelf/elfutils.

Signed-off-by: Cody P Schafer <cody@...ux.vnet.ibm.com>
Cc: David Hansen <dave@...ux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Matt Hellsley <matthltc@...ibm.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-10-git-send-email-cody@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/symbol-elf.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index a2e994e..a9a194d 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -129,6 +129,10 @@ static Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
 	Elf_Scn *sec = NULL;
 	size_t cnt = 1;
 
+	/* Elf is corrupted/truncated, avoid calling elf_strptr. */
+	if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL))
+		return NULL;
+
 	while ((sec = elf_nextscn(elf, sec)) != NULL) {
 		char *str;
 
-- 
1.7.1

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